Our goal is to develop novel methods of artificially induced cell fusion to meet the growing needs of biomedicine and biotechnology. The molecular mechanisms of polyethylene glycol and electric field induced membrane fusion have been better understood, owing to our efforts and those of others in the past. This knowledge is to be used as basis to significantly improve the efficiency, versatility and controllability of new fusion methods. To improve fusion efficiency, cell contacts will be manipulated in centrifugation pellets, in overlaying monolayers, and in PEG-induced aggregates. The timing and degree of colloidal osmotic swelling after the pulse application, and the number of pulses will be controlled precisely to maximize fusion and viability, based on known membrane breakdown and cell swelling characteristics. By reducing cell lysis with polymers, and increasing contacts between heterogeneous fusion partners, we aim to induce efficient fusions between cells of different sizes, between suspending, adherent and tissue cells, as well as between liposomes, membrane vesicles and cells. Cationic lipids and PEG-conjugated lipids will be utilized to fine-tune the cell-liposome adhesion. A novel two phase polymer method will be used to enhance cell loading by electroporation. Highly efficient and controllable fusion methods will contribute to human hybridoma formation as well as in vitro gene transfer to human cell targets where cell sources are limited. Effective loading of targeted cells, or transferring membrane components to targeted cell surfaces by new fusion methods will be valuable in research and medical applications.